Aeroacoustic imaging experiments of air-frame noise in lined wall closed-section wind tunnel

The experimental technique of aeroacoustic imaging is critical to validate the low noise design methods of the civil transportation. In this work, we demonstrate this experimental method in a classical closed-section wind tunnel, which has been acoustically modified by installing liners to solid walls of the test section. The details of the associated acoustic modification and the aeroacoustic imaging method are introduced in this paper. The acoustic test performance is carefully examined by assessing background noise reductions and beamform-ing results. The experimental results suggest that the proposed acoustic modification could suppress background noise by 5 dB at 40 to 80 m/s flow speeds. The beamforming results clearly identify the dominant airframe noise sources at landing gears and high lift devices. The experimental results agree fairly well with preceding computational and empirical predictions. Hence, the proposed test method and acoustic modification design are effective, which could be considered to extend capabilities of most existing closed-section wind tunnels for aeroacoustic applications.EI